Tool Radius Research Articles

Optimization of Forming Parameters in Incremental Sheet Forming of AA3003-H18 Sheets Using Taguchi Method.

The surface finish is an important characteristic in the incremental sheet forming (ISF) process and is often influenced by numerous factors within the forming process. Therefore, this research was aimed at identifying the optimal forming parameters through the Taguchi method to produce high-quality formed products. The forming tool radius, spindle speed, vertical step increment, and feed rate were chosen as forming parameters in the experimental design, with surface roughness as the response variable. Taguchi L16 orthogonal array design and analysis of variance (ANOVA) test were used to identify the parameter’s optimal settings and examine the statistically significant parameters on the response, respectively. Results confirmed that a significant reduction in surface roughness occurred with a drop in vertical step size and an increase in feed rate. In detail, the vertical step size has the most significant influence on the surface roughness, followed by the feed rate and the forming tool radius. In conclusion, the optimum level settings were obtained: forming tool radius at level 3, spindle speed at level 1, vertical step size at level 1, and feed rate at level 4. Additionally, confirmation experiment results based on the optimal settings indicated a good agreement against the experimental observation. Further, the response surface methodology (RSM) was also exploited to devise a mathematical model for predicting the surface roughness. The results comparison confirmed that both techniques could effectively improvise the surface finish.

Development of a Surface Roughness Prediction Model for Slow Tool Servo Turning Machining

To investigate the effect of slow tool servo turning process parameters on surface roughness, we es-tablished a high precision surface roughness prediction model. A guide to the selection of turning process parameters was compiled, and a turning test was conducted based on a response surface method (RSM) central composite design. ANOVA explores the influence law of process parameters on surface roughness. A RSM BP neural network model, and MEA-BP surface roughness model were established and the prediction performance of the three models was evaluated. The results show that the significant process parameters affecting surface roughness are tool radius, discrete angle, feed rate, and cutting depth in descending order; and the prediction errors of RSM, BP, and MEA-BP are 11.41%, 19.67%, and 5.54%. This suggests that the MEA-BP model has the highest prediction accura-cy with the same test data, RSM is second, whilst the single BP model struggles to capture multiple data characteristics and its prediction accuracy is poor. In addition, MEA can effectively solve the BP model falling into local optimum and improve the model prediction accuracy.

Effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the contact zone with a cylindrical surface

This paper aims to determine the effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the center of elastoplastic deformation and residual stresses in the hardened zone of the surface layer of cylindrical workpieces. A mathematical model of local loading was constructed using the finite element method and AN-SYS software. This model was used to determine the values of temporary and residual stresses and deformations, as well as the depth of plastic zone, depending on the sector radius of the working tool. The simulation results showed that, under the same loading of a cylindrical surface, working tools with different sector radii create different maximum tempo-rary and residual stresses. An assessment of the stress state was carried out for situations when the surface layer of a product is treated by workpiece-deforming tools with a different shape of the working edge. It was shown that, compared to a flat tool, a decrease in the radius of the working sector from 125 to 25 mm leads to an increase in the maximum temporary and residual stresses by 1.2–1.5 times, while the plastic zone depth increases by 1.5–2.4 times. The use of a working tool with a flat surface for hardening a cylindrical workpiece ensures minimal temporary residual stresses, com-pared to those produced by a working tool with a curved surface. A decrease in the radius of the working sector leads to an increase in temporary residual stresses by 2–7%. The plastic zone depth ranges from 1.65 to 2.55 mm when chang-ing the sector radius of the working tool.

Predicting maximum force in SPIF for different materials

Knowing the importance of predicting acting forces during the formation process, our research has conducted 27 Single Point Incremental Forming (SPIF) experiments in hyperboloid format, followed by Finite Element Method (FEM) simulations and regression equations were determined to estimate the maximum axial force in the process. ANOVA analysis of variance was used to determine the significance of material parameters in the maximum axial force response. A multiple linear regression model was constructed to estimate the maximum axial force in the SPIF process. After the experiments, we were able to identify that the maximum axial force increases according to an increase in tool radius, sheet initial thickness, and strength coefficient values, as well as according to the decrease in the strain-hardening exponent. The FEM simulations are in agreement with the experimental values found, and the linear regression model has proven to be efficient to describe results, with R2 of 98.85% and a maximum percentage error of 11.5%.

Nanomachining characteristics of textured polycrystalline NiFeCo alloy using molecular dynamics

This work investigates the grinding process of a polycrystalline NiFeCo alloy through molecular dynamics (MD) simulation. The important factors that affect the grinding mechanics are cautiously investigated by analyzing the grinding force, resistance coefficient, local stress and strain, temperature, surface morphology, the evolution of structure and dislocation, which contain grinding velocity, machining depth, tool radius, and surface texture. The result shows that a higher machining velocity, greater grinding depth and tool radius lead to a larger grinding force and chipping volume, as well as a higher temperature of the substrate. While the grinding force, chipping volume, and temperature are the largest in the grinding of smooth surface compared to other surface textures due to the greater surface density. Moreover, the morphology of surface texture powerfully influences the pile-up volume, but slightly affects the shape of groove. The local shear strain and stress play a significant role in the grinding that explains the deformation mechanism in the substrate under the high pressure of cutting tool, and the grain boundary in polycrystalline is the control factor in the deformation behavior. Notably, the analysis of structure and dislocation evolution reveals that the nucleation and movement of dislocation caused plastic strain during the grinding show clearly the mechanism of subsurface damage. Besides, the dislocation motion is eliminated by grain boundary or interacts with each other to form new dislocation.

Feasibility study of single-crystal silicon ductile-regime turning via fast tool servo

Due to the material properties of single-crystal silicon, it is difficult to achieve high-efficiency processing in conventional turning. Fast tool servo (FTS) turning has emerged as a favorable technology for processing brittle materials. This paper investigates the tool radius, feed speed, and cutting depth effects on the maximum undeformed chip thickness (MUCT). A high-frequency low-coupling FTS system is designed for processing experiments. Effects of the tool rake angle, tool radius, cutting speed, and vibration frequency on the critical undeformed chip thickness (CUCT) are explored in this paper. Experimental results indicate FTS technology can increase the CUCT from 80 nm to 580 nm. Surface and subsurface morphology tests of conventional and FTS single-crystal silicon cutting verify that FTS technology can obtain an optical surface roughness of 5 nm and lower subsurface damage. Moreover, FTS turning can reduce tool wear. Lastly, through Raman spectroscopy analysis, the amorphous phase remaining on the machined surface is lower when FTS turning is employed.

Mechanistic modeling of cutting forces in high-speed microturning of titanium alloy with consideration of nose radius

Microturning is a micromechanical machining process used to produce microcylindrical or axially symmetrical parts. Microcylindrical parts are mainly used in microfluidic systems, intravenous micromotors, microsurgical applications, optical lens applications, and microinjection systems. The workpiece diameter is very small in microturning and therefore is greatly affected by the cutting forces. For this reason, it is important to predict the cutting forces when machining miniature parts. In this study, an analytical mechanistic model of microturning is used to predict the cutting forces considering the tool nose radius. In the semi-empirically developed mechanistic model, the tool radius was considered. A series of semi-orthogonal microturning cutting tests were carried out to determine the cutting and edge force coefficients. The mechanistic model was generalized depending on the cutting speed and depth of cut by performing multilinear regression analysis. In the study, the depth of cut (ap = 30–90 µm) and feed values (f = 0.5–20 µm/rev) were selected considering the nose radius and edge radius of the cutting tool. The experiments were carried out under high-cutting speeds (Vc = 150–500 m/min) and microcutting conditions. Ti6Al4V alloy was used as the workpiece material and the tests were carried out under dry cutting conditions. Validation tests for different cutting parameters were carried out to validate the accuracy of the developed mechanistic model. The results showed that the difference between the mechanistic model and the experimental data was a minimum of 3% and a maximum of 24%. The maximum difference between the experimental and the model usually occurs in forces in the tangential direction. It has been observed that the developed model gives accurate results even at a depth of cut smaller than the nose radius and at feed values smaller than the edge radius.

Friction and Wear Behavior of Deep Drawing Tools Using Volatile Lubricants Injected Through Laser-Drilled Micro-Holes

In deep drawing processes, the use of lubricants is mandatory in order to prevent wear on tools and surface damage to the formed sheet metal components. Here, frequently used lubricants are synthetic and mineral oils, emulsions, and waxes. However, these conventional lubricants have to be applied to the sheet material prior to the forming operation and removed afterwards by cleaning processes. Additionally, the lubricants often contain substances that are harmful to the environment and to human health. To counteract these economic and ecological disadvantages, research is currently being conducted on a novel tribological system. For this, volatile media such as liquid carbon dioxide and gaseous nitrogen are being used, and are introduced directly into the friction zones between the tool and the sheet metal material during deep drawing under high pressure through special laser-drilled micro-holes. This paper covers the latest investigations and findings regarding the design of flow-optimized micro-holes, the laser drilling process, the friction characterization on tool radii, and the tool wear to be expected when using the lubrication medium CO2.

Tool Path Generation for Five-Axis Controlled Machining of Free-Form Surfaces Using a Barrel Tool Considering Continuity of Tool Postures

This study aims to improve the efficiency of free-form surface machining using a five-axis controlled machine tool and a barrel tool. The barrel tool has cutting edges with curvatures smaller than its radius; thus, its pick feed width is larger than that of a conventional ball end mill with the same tool radius. Therefore, the machining efficiency can be improved. Barrel tools can be effectively utilized in a five-axis controlled machine tool. When five-axis controlled machining, tool interference may occur, which should be avoided during actual machine operation. Additionally, a sudden change in tool posture adversely affects the quality of the machined surface. This paper proposes a method to obtain the cutting points that render cusp heights below the target value. A method for generating an interference-free tool path, in which the tool posture changes continuously, is also proposed. The usefulness of the developed methods was confirmed through machining simulations.

Finite element study on spinning process of an aluminium tube

This article aims to have a glimpse into the effect of the spinning tool parameters (focusing on its diameter, attack angle, nose radius, and feed) by applying the explicit code of the commercial finite element analysis software LS-DYNA. The preliminary results show that the greater the axial feed, the greater the loads generated in the axial, the tangential, and the radial directions. At the same time, the larger the axial feed, the more the elements are parallel to the axial direction from the inflection point to the tube opening. Furthermore, using a larger axial feed will also cause the flaring of the tube opening and make the flaring more obvious. In addition, using a larger axial feed will not only cause a greater material accumulation in front of the attack angle, but also a larger material accumulation at the tangential rear of the nose radius. Moreover, the greater the attack angle, the greater the axial load. There is no further significant effect of the corner radius of the spinning tool on the spinning load.

The Performance of 3D Printed Polymer Tools in Sheet Metal Forming

Additively manufactured polymer tools are evaluated for use in metal forming as prototype tools and in the attempt to make sheet metal more attractive to small production volumes. Printing materials, strategies and accuracies are presented before the tools and tested in V-bending and groove pressing of 1 mm aluminum sheets. The V-bending shows that the tools change surface topography during forming until a steady state is reached at around five strokes. The geometrical accuracy obtained in V-bending is evaluated by the spring-back angle and the resulting bend radius, while bending to 90° with three different punch nose radii. The spring-back shows additional effects from the elastic deflection of the tools, and the influence from the punch nose radius is found to be influenced by the printing strategy due to the ratio between tool radius and the printed solid shell thickness enclosing the otherwise less dense bulk part of the tool. Groove pressing shows the combined effect of groove heights and angular changes due to spring-back. In all cases, the repeatability is discussed to show the potential of tool corrections for obtaining formed parts closer to nominal values.

Principle and Application of the Ball End Mill Tool Radius Compensation for NURBS Curve Swept Surfaces Based on 3-Axis CNC Milling Machines

Principle and Application of the Ball End Mill Tool Radius Compensation for NURBS Curve Swept Surfaces Based on 3-Axis CNC Milling Machines

Analysis of dimensional accuracy for micro-milled areal material measures with kinematic simulation

The calibration of areal surface topography measuring instruments is of high relevance to estimate the measurement uncertainty and to guarantee the traceability of the measurement results. Calibration structures for optical measuring instruments must be sufficiently small to determine the limits of the instruments.Besides other methods, micro-milling is a suitable process for manufacturing areal material measures. For the manufacturing by micro-milling with ball end mills, the tool radius (effective cutter radius) is the corresponding limiting factor: if the tool radius is too large to penetrate the concave profile details without removing the surrounding material, deviations from the target geometry will occur. These deviations can be detected and excluded before experimental manufacturing with the aid of a kinematic simulation.In this study, a kinematic simulation model for the prediction of the dimensional accuracy of micro-milled areal material measures is developed and validated. Subsequently, a radius study is conducted to determine how the tool radius r of the tool influences the dimensional accuracy of an areal crossed sinusoidal (ACS) geometry according to ISO 25178-70 [1] with a defined amplitude d and period length p. The resulting theoretical surface texture parameters are evaluated and compared to the target values. It was shown that the surface texture parameters deviate from the nominal values depending on the effective cutter radius used. Based on the results of the study, it can be determined with which effective tool radius the measurands Sa and Sq of the material measures are best met. The ideal effective radius for the application considered is between 50 and 75 μm.

Impact of process variables on surface roughness in negative incremental forming process

A pivotal development of the obsolescence of conventional methods of sheet forming has enhanced the need of augmenting an agile and novel method of fabricating the tailored components according to the requirements of customers and users. Moreover, businessmen are interested to promote their businesses by manufacturing the tailored and customized parts of intricated and complex geometries at a lower cost and with negligible waste. Single Point Incremental Forming (SPIF), also known as “negative incremental forming”, avoids the direct use of any kind of specific die-sets and produces the user-ready parts. The investigation of the surface quality of the formed specimen is important to study the suitability of this process for industrial applications. This paper explores the effects of the interactions of tool radius and forming angle on the surface roughness of parts formed by the SPIF process. A full factorial approach was taken into account as DOE. The average roughness was found to rise with the rise in forming an angle. On the other hand, the increase in tool diameter resulted in the decrease of Ra value of formed components because the increase in the tool diameter allows the decrease in the waviness on the surface of the specimen. It was observed that the Ra value of formed components was decreased by 83.87% when the experimental condition was changed from the combination of higher levels of wall angle (68°) and lower level of tool diameter (7.52 mm) to the combination of lower levels of wall angle (60°) and a higher level of tool diameter (19.50 mm).

A Comprehensive Micro-Milling Force Model for a Low-Stiffness Machining System

Abstract Micro-milling is widely used in various crucial fields with the ability of machining micro- and meso-scaled functional structures on various materials efficiently. However, the micro-milling force model is not comprehensively developed yet when tool feature sizes continually decrease to under 200 µm in a low-stiffness system. This paper proposes an analytical force model considering the influence of tool radius, size effect, tool runout, tool deflection, and the actual trochoidal trajectories and the interaction of historical tool teeth trajectories (IHTTT). Different micro-milling status are recognized by analyzing the cutting process of different tool teeth. Conditions of single-tooth cutting status are determined by a proposed numerical algorithm, and entry angle and exit angle are analyzed under various cutting conditions for the low-stiffness system. Three micro-milling status, including single-tooth cutting status, are distinguished based on the instantaneous undeformed chip thickness resulting in three types of material removal mechanisms in predicting micro-milling force components. Discontinuous change rates of undeformed chip thickness are found in the low-stiffness micro-milling system. The proposed micro-milling force model is then verified through experiments of micro slot milling Elgiloy alloy with a 150-μm-diametrical two-teeth micro-end mill. The experimental results show a root-mean-square error (RSME) of 0.092 N in the predicted resultant force, accounting for approximately 5.12% of the measured force, by which the proposed theoretical model is verified to be of good prediction accuracy.

Fabrication and evaluation of complicated microstructures on cylindrical surface

Various items of roll molds are popularly used to fabricate different kinds of optical films for optoelectronic information and other new and high-tech fields, while the fabrication and evaluation of optical microstructures on the cylindrical roller surface is more difficult than ecumenic manufactured products. This paper investigates the machinability of microstructures on the roll based on a fast tool servo (FTS) system. First, the flexible hinge holder for FTS is designed and its structure parameters are optimized with finite element analysis and fatigue reliability theory. Then the tool radius compensation algorithm for complicated microstructures is deduced based on the surface fitting and bilinear interpolation algorithm of discrete data. Meanwhile, the evaluation index and method are proposed by the medium section method. Finally, a machining test of aspheric arrays on aluminum cylindrical surface is carried out, and the high quality of the microstructure indicates that the proposed method is able to fabricate optical microstructures.

Compensating the springback of ultra-high-strength steel parts by specific stress superposition during sheet metal forming

Ultra-high-strength steel sheets offer considerable advantages in car body construction regarding the permanent requirements for vehicle weight reduction as well as the increase in crashworthiness of sheet metal parts. However, when forming such sheet metal materials, the main problem relates to their distinctive springback behaviour, which occurs after the formed part has been released. This paper shows a methodology for springback compensation based on the superposition of stresses acting in the meridian direction of the formed sheet metal part. These stress superposition effects are induced via the tool radii by alternating blank draw-in during deep drawing. As a result, the workpiece areas contacting the punch radii during the deep drawing process are subjected to repeated bending and unbending. In order to analyse occurring stress superposition effects and their influence on springback appearance, simulation was performed using the FE-code LS-Dyna. Furthermore, an optimal blank draw-in kinematic could be defined using the forming simulation, which significantly reduced springback of a double-curved hat-shaped component made of DP 980 steel sheet after forming. Finally, this numerically determined methodology for springback compensation has been experimentally proved using tool that enables alternating blank draw-in during sheet metal forming.

Surface texture generation using high-feed milling with spindle speed modulation

This paper presents a new surface texturing technique using ball-end milling with high feed speed and spindle speed modulation. The ratio between feed-rate and cutting tool radius is in the range of 0.2–0.4, which is much larger than the ratio in conventional milling. Sinusoidal modulation signal is added, so the spindle speed becomes time-varying in order to generate different texture profiles. The cutting tool kinematics are modeled considering the tool-tip run-out and deflection due to cutting forces. The effects of amplitude and frequency of the modulation signal on tool-tip trajectories and surface textures are simulated and analyzed. The relationship between the micro features of the surface texture and the process parameters are investigated. Surface texturing experiments are conducted based on the proposed technique, and tribology tests are performed on the textured surface. It is shown that the textured surfaces present frictional anisotropy, which depends on the process conditions and modulation parameters. The proposed technique is able to achieve fast generation of various surface textures without additional instrumentation, and the final texture geometry is controllable based on the presented kinematics model.

Geometrical consideration for mechanical contact between rolling circle and surface roughness as an improvement to the surface profile

This paper describes measurement methods of surface profiles that improve contact-type displacement sensor outputs by focusing on the contact point between the sphere tip of the sensor and the rough surface. We examined the geometry of a surface profile model and compared measurements using various methods with the measurement using a roughness meter. The spherical tip of the contact type displacement sensor touches the measurement surface and detects the displacement. The sphere tip radius of a typical contact-type displacement sensor ranges from 1–3 mm, causing the roughness curve to be “filtered” by the radius of the sphere. Three methods for estimating the valley portion of the surface profile are evaluated in this study: a) linear approximation of the concave portion of the surface profile, b) function approximation of the concave portion, and c) using the known nose radius of the machining tool. The following sphere tip radii were used to measure actual surface profiles: 0.25 mm, 0.5 mm, 1.0 mm and 1.5 mm. Given the conditions of the experimental model, we found that surface profiles with a roughness that approximates a predictable curve can be measured with a high degree of accuracy.

Influence of Tool Geometry and Process Parameters on the Properties of Friction Stir Spot Welded Multiple (AA 5754 H111) Aluminium Sheets.

Friction stir spot welding is an emerging spot-welding technology that offers opportunities for joining a wide range of materials with minimum energy consumption. To increase productivity, the present work addresses production challenges and aims to find solutions for the lap-welding of multiple ultrathin sheets with maximum productivity. Two convex tools with different edge radii were used to weld four ultrathin sheets of AA5754-H111 alloy each with 0.3 mm thickness. To understand the influence of tool geometries and process parameters, coefficient of friction (CoF), microstructure and mechanical properties obtained with the Vickers microhardness test and the small punch test were analysed. A scanning acoustic microscope was used to assess weld quality. It was found that the increase of tool radius from 15 to 22.5 mm reduced the dwell time by a factor of three. Samples welded with a specific tool were seen to have no delamination and improved mechanical properties due to longer stirring time. The rotational speed was found to be the most influential parameter in governing the weld shape, CoF, microstructure, microhardness and weld efficiency. Low rotational speeds caused a 14.4% and 12.8% improvement in joint efficiency compared to high rotational speeds for both tools used in this investigation.